Expandable cardiac shunt

ABSTRACT

Disclosed are cardiac shunts and method of delivery, and in particular, to a shunt to reduce elevated left atrial pressure (LAP). The methods include forming a puncture hole between the left atrium and the coronary sinus, widening the puncture hole, and placing an expandable shunt within the widened puncture hole. A first catheter having a side-extending needle may be used to form a puncture into the left atrium. A second catheter extends along a guidewire and an expandable shunt with distal and proximal flanges is expelled therefrom into the puncture. The shunt defines a blood flow passage therethrough that permits shunting of blood from the left atrium to the coronary sinus when the LAP is elevated. The shunt is desirable formed of a super-elastic material and manipulated with control rods. The shunt defines a tilted flow tube that facilitates collapse into the catheter.

RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. 119 to both U.S.Provisional Application Ser. No. 62/262,052, filed Dec. 2, 2015 and U.S.Provisional Application Ser. No. 62/238,229, filed Oct. 7, 2015, thecontents of which are expressly incorporated herein.

FIELD OF THE INVENTION

The present invention relates generally to cardiac shunts and systemsand methods of delivery, and in particular, to a shunt to reduce leftatrial pressure.

BACKGROUND OF THE INVENTION

In vertebrate animals, the heart is a hollow muscular organ having fourpumping chambers: the left and right atria and the left and rightventricles, each provided with its own one-way valve. The natural heartvalves are identified as the aortic, mitral (or bicuspid), tricuspid andpulmonary, and are each mounted in an annulus comprising dense fibrousrings attached either directly or indirectly to the atrial andventricular muscle fibers. Each annulus defines a flow orifice. The fourvalves ensure that blood does not flow in the wrong direction during thecardiac cycle; that is, to ensure that the blood does not back flowthrough the valve. Blood flows from the venous system and right atriumthrough the tricuspid valve to the right ventricle, then from the rightventricle through the pulmonary valve to the pulmonary artery and thelungs. Oxygenated blood then flows through the mitral valve from theleft atrium to the left ventricle, and finally from the left ventriclethrough the aortic valve to the aorta/arterial system.

Heart failure is a common and potentially lethal condition affectinghumans, with sub-optimal clinical outcomes often resulting in symptoms,morbidity and/or mortality, despite maximal medical treatment. Inparticular, “diastolic heart failure” refers to the clinical syndrome ofheart failure occurring in the context of preserved left ventricularsystolic function (ejection fraction) and in the absence of majorvalvular disease. This condition is characterized by a stiff leftventricle with decreased compliance and impaired relaxation, which leadsto increased end-diastolic pressure. Approximately one third of patientswith heart failure have diastolic heart failure and there are very few,if any, proven effective treatments.

Symptoms of diastolic heart failure are due, at least in a large part,to an elevation in pressure in the left atrium. Elevated Left AtrialPressure (LAP) is present in several abnormal heart conditions,including Heart Failure (HF). In addition to diastolic heart failure, anumber of other medical conditions, including systolic dysfunction ofthe left ventricle and valve disease, can lead to elevated pressures inthe left atrium. Both Heart Failure with Preserved Ejection Fraction(HFpEF) and Heart Failure with Reduced Ejection Fraction (HFrEF) canexhibit elevated LAP. It has been hypothesized that both subgroups of HFmight benefit from a reduction in LAP, which in turn reduces thesystolic preload on the left ventricle, Left Ventricular End DiastolicPressure (LVEDP). It could also relieve pressure on the pulmonarycirculation, reducing the risk of pulmonary edema, improving respirationand improving patient comfort.

Pulmonary hypertension (PH) is defined as a rise in mean pressure in themain pulmonary artery. PH may arise from many different causes, but, inall patients, has been shown to increase mortality rate. A deadly formof PH arises in the very small branches of the pulmonary arteries and isknown as Pulmonary Arterial Hypertension (PAH). In PAH, the cells insidethe small arteries multiply due to injury or disease, decreasing thearea inside of the artery and thickening the arterial wall. As a result,these small pulmonary arteries narrow and stiffen, causing blood flow tobecome restricted and upstream pressures to rise. This increase inpressure in the main pulmonary artery is the common connection betweenall forms of PH regardless of underlying cause.

Despite previous attempts, there is a need for an improved way to reduceelevated pressure in the left atrium, as well as other susceptible heartchambers such as the pulmonary artery.

SUMMARY OF THE INVENTION

The present application discloses a method and several deviceembodiments that allow for elevated Left Atrial Pressure (LAP) to bereduced by shunting blood from the left atrium to the coronary sinus. Bycreating an opening between the left atrium and the coronary sinus,blood will flow from the higher pressure left atrium (usually >8 mmHg)to the lower pressure coronary sinus (usually <8 mmHg).

Using catheter-based instruments, the surgeon creates a puncture holebetween the left atrium and the coronary sinus, and places an expandableshunt within the puncture hole. A first puncture catheter having aside-extending needle may be used to form a puncture into the leftatrium. A second delivery catheter extends along a guidewire and anexpandable shunt with distal and proximal flanges is expelled therefrominto the puncture. The shunt defines a blood flow passage therethroughthat permits shunting of blood from the left atrium to the coronarysinus when the LAP is elevated. The shunt is desirable formed of asuper-elastic material and defines a tilted flow tube that facilitatescollapse into the catheter.

The expandable blood flow shunts described herein are formed of anelastic material and configured to be inserted into a puncture wound ina tissue wall between two anatomical chambers and expand from acollapsed state to an expanded state to maintain a blood flow openingtherebetween, the tissue wall defining a reference plane generallyperpendicular to the opening.

In a first embodiment, the shunt in an expanded state includes a centralflow tube defined by an opposed pair of lateral side walls formed bystruts extending between an opposed pair of end walls formed by struts,the central flow tube defining a central axis therethrough angled from areference axis extending perpendicular through the reference plane. Twodistal flanges formed by struts each attach to a first axial end of thecentral flow tube, the distal flanges extending away from one another inopposite longitudinal directions generally parallel to the referenceplane. Two proximal flanges formed by struts each attach to a secondaxial end of the central flow tube opposite the first end, the proximalflanges extending away from one another in opposite longitudinaldirections generally parallel to the reference plane. The proximalflanges extend in the same directions as the distal flanges such thateach proximal flange parallels one of the distal flanges to form aclamping pair of flanges with a gap therebetween sized to clamp onto thetissue wall.

In a second embodiment, the shunt in an expanded state includes acentral flow tube defined by an opposed pair of lateral side wallsformed by struts extending between an opposed pair of end walls formedby struts, the side walls and end walls together defining a tubularlattice and the central flow tube defining a central axis therethrough.Two distal flanges formed by struts connect to struts in the centralflow tube at a first axial end thereof, the distal flanges extendingaway from one another in opposite longitudinal directions generallyparallel to the reference plane, wherein there is one long and one shortdistal flange. Two proximal flanges formed by struts connect to strutsin the central flow tube at a second axial end thereof opposite thefirst end, the proximal flanges extending away from one another inopposite longitudinal directions generally parallel to the referenceplane. There is one long and one short proximal flange, the proximalflanges extending in the same directions as the distal flanges such thateach proximal flange parallels one of the distal flanges to form aclamping pair of flanges with a gap therebetween sized to clamp onto thetissue wall. Further, the long distal flange and the short proximalflange form a clamping pair and the short distal flange and the longproximal flange form a clamping pair.

In a third embodiment, the shunt in an expanded state includes a centralflow tube comprising an opposed pair of lateral side walls formed bystruts that define open cells extending between an opposed pair of endwalls formed by struts that define open cells. The side walls and endwalls together define a tubular lattice and the central flow tubedefines a central axis therethrough, wherein each side wall includesupper and lower rows of cells defined by the corresponding strutsstacked along the central axis. Two distal flanges formed by strutsconnect to struts in the central flow tube at a first axial end thereof,the distal flanges extending away from one another in oppositelongitudinal directions generally parallel to the reference plane. Twoproximal flanges formed by struts connect to struts in the central flowtube at a second axial end thereof, the proximal flanges extending awayfrom one another in opposite longitudinal directions generally parallelto the reference plane. The proximal flanges extend in the samedirections as the distal flanges such that each proximal flangeparallels one of the distal flanges to form a clamping pair of flangeswith a gap therebetween sized to clamp onto the tissue wall.Additionally, the two rows of cells in each side wall stop short of theopposed end walls of the central flow tube to define spaces therebetweensuch that a first end wall directly connects only to the upper row ofcells while a second end wall directly connects only with the lower rowof cells.

In any of the shunt embodiment described herein, the struts of each ofthe proximal and distal flanges are desirably curved such that theflanges in each clamping pair of flanges initially curve away from eachother and then converge toward each other at a terminal end thereof.Further, each clamping pair of flanges may include flanges of differentlengths. Preferably, exemplary shunts have a maximum lateral widthdefined by the central flow tube. Additionally, the central flow tube ofthe shunts as viewed along their central axes are desirably circular. Ina preferred embodiment, when the shunts transition from the collapsed tothe expanded state a first flange in each clamping pair of flangesrotates outward more than 90° and a second flange in the same clampingpair of flanges rotates outward less than 90°. The struts of the lateralside walls may form connected parallelograms defining open cellstherein. More particularly, each side wall may include upper and lowerrows of parallelogram-shaped cells defined by the corresponding strutsand stacked along the central axis, wherein the upper row connects to afirst end wall only and the lower row connects to a second end wallonly.

The present application further discloses a system for deploying any ofthe expandable shunts described above into a puncture wound in a tissuewall to maintain an opening therebetween, the tissue wall defining areference plane. The system includes a delivery catheter having aproximal handle, an outer sheath surrounding an inner sheath. The shuntis mounted in a collapsed configuration on the inner sheath with theouter sheath surrounding and maintaining the shunt in a collapsed statewith the proximal flanges oriented toward the handle. A pair ofactuating rods extend from the handle distally through the inner sheath,each of which engages one of the proximal flanges of the shunt, theactuating rods being linearly slidable within the inner sheath. Thesystem also has a puncture catheter with a proximal handle, an elongatedflexible body having a distal tip, a guidewire lumen extending throughthe body from the handle to the distal tip, and a needle lumen extendingthrough the body from the handle to a side port located near the distaltip. Finally, the system includes an elongated puncture sheath with alumen and an elongated needle having a sharp tip sized to fit throughthe puncture sheath lumen such that the sharp tip projects therefrom.The puncture sheath is sized to pass through the needle lumen of thepuncture catheter and project out of the side port to form a puncture ina tissue wall. The system may further include an expandable member sizedto pass through the needle lumen and project out of the side port intothe puncture, the expandable member being radially expandable to widenthe puncture. The system may further include an expandable anchoringmember located on the flexible body opposite the side port. A pair ofradiopaque markers are preferably located distal and proximal to theexpandable anchoring member on the side port side of the flexible body.The puncture catheter proximal handle may have an advancer fordisplacing the puncture sheath and a locking nut that fixes the puncturesheath relative to the handle.

An alternative system for deploying the expandable shunts describedherein into a puncture wound in a tissue wall to maintain an openingtherebetween is disclosed, the wall defining a reference plane. Thesystem includes a delivery catheter having a proximal handle, an outersheath surrounding an inner sheath. The shunt is mounted in a collapsedconfiguration on the inner sheath with the outer sheath surrounding andmaintaining the shunt in a collapsed state with the proximal flangesoriented toward the handle. A pair of actuating rods extend from thehandle distally through the inner sheath, each of which engages one ofthe proximal flanges of the shunt, the actuating rods being linearlyslidable within the inner sheath. A puncture catheter has a proximalhandle, an elongated flexible body having a distal tip, a guidewirelumen extending through the body from the handle to the distal tip, anda needle lumen extending through the body from the handle to a side portlocated near the distal tip. The puncture catheter further includes anexpandable anchoring member located on the flexible body opposite theside port. Finally, a puncture sheath is sized to pass through theneedle lumen and project out of the side port to form a puncture in atissue wall. The elongated puncture sheath preferably has a lumen and anelongated needle having a sharp tip sized to fit through the puncturesheath lumen such that the sharp tip projects therefrom. The alternativesystem may further include an expandable member sized to pass throughthe needle lumen and project out of the side port into the puncture, theexpandable member being radially expandable to widen the puncture.Further, a pair of radiopaque markers are preferably located distal andproximal to the expandable anchoring member on the side port side of theflexible body. The alternative system also may have an elongatedpuncture sheath having a lumen and an elongated needle having a sharptip sized to fit through the puncture sheath lumen such that the sharptip projects therefrom, the puncture sheath being sized to pass throughthe needle lumen of the puncture catheter and project out of the sideport to form a puncture in a tissue wall. The puncture catheter proximalhandle may have an advancer for displacing the puncture sheath and alocking nut that fixes the puncture sheath relative to the handle.

In either shunt deployment systems described above, the central flowtube of the shunt is preferably defined by an opposed pair of lateralside walls formed by struts extending between an opposed pair of endwalls formed by struts, the central flow tube defining a central axistherethrough angled from a reference axis extending perpendicularthrough the reference plane. The shunt is desirably mounted in itscollapsed configuration within a recess near a distal end of the innersheath with the central axis therethrough coinciding with a longitudinalaxis of the inner sheath at the recess.

The present application also contemplates a method of deploying any ofthe shunts described herein into a puncture wound in a tissue wall tomaintain an opening therebetween, the wall defining a reference plane.The method includes the steps of:

establishing access to a patient's vasculature;

advancing a first guidewire through the vasculature, into the rightatrium and into the coronary sinus;

advancing a first catheter having a side-extending needle along thefirst guidewire until the side-extending needle is positioned within thecoronary sinus adjacent the left atrium;

expanding a stabilizing anchor from the first catheter into contact withthe coronary sinus wall, the stabilizing anchor being located on thefirst catheter opposite a needle port in a side of the first catheter;

forming a puncture hole in a wall between the left atrium and thecoronary sinus by advancing the side-extending needle from the needleport in the first catheter;

advancing a second guidewire through a lumen in the side-extendingneedle to remain extending into the left atrium;

withdrawing the first catheter;

advancing a second catheter along the second guidewire until a distaltip thereof is positioned through the puncture and within the leftatrium, the second catheter carrying the shunt

partially expelling the shunt from within the catheter such that thedistal flanges expand on a distal side of the tissue wall;

retracting the second catheter until the distal flanges contact thedistal side of the wall;

fully expelling the shunt from within the catheter by expelling theproximal flanges such that the proximal flanges expand on a proximalside of the tissue wall and the clamping pairs hold the shunt in placein the tissue wall so as to define a blood flow passage therethrough.

The method preferably also includes widening the puncture hole using anexpandable member that projects from the needle port. The tissue wall ispreferably located between the coronary sinus and the left atrium andplacing the shunt in the tissue wall permits shunting of blood betweenthe left atrium and coronary sinus.

A further understanding of the nature and advantages of the inventionwill become apparent by reference to the remaining portions of thespecification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of the present invention will become appreciatedas the same become better understood with reference to thespecification, claims, and appended drawings wherein:

FIG. 1 is an overview of a heart illustrating how guidewires andcatheters may be maneuvered in and around the heart to deploy expandableshunts of the present application;

FIG. 2 shows a first catheter extending from the superior vena cava tothe coronary sinus of the heart;

FIGS. 3A-3V are schematic views of steps in making a puncture holethrough a wall of the coronary sinus and placement of a shunt betweenthe coronary sinus and left atrium, as seen looking down on a section ofthe heart with the posterior aspect down;

FIGS. 4A-4H illustrates a sequence of deployment of an exemplaryexpandable shunt through a sheath using a pair of actuating rods;

FIGS. 5A-5C are several views of the expandable shunt being retractedinto the delivery catheter;

FIGS. 6A-6D are perspective, elevational, and plan views of theexemplary expandable shunt in an expanded configuration, FIG. 6E is aview looking through a central flow tube along an angle, and FIG. 6F isa view similar to FIG. 6E through an alternative shunt having anoval-shaped flow tube;

FIGS. 7A and 7B are elevational views of the exemplary expandable shuntillustrating certain dimensions and advantageous structural features;

FIGS. 8A-8D are flattened and partial perspective views of the exemplaryexpandable shunt highlighting certain other advantageous features;

FIGS. 9A-9D are perspective and orthogonal views of the exemplaryexpandable shunt in a collapsed configuration for delivery through anaccess sheath or catheter;

FIG. 10 is a schematic view of an access sheath passing through a tissuewall with the exemplary expandable shunt therein in a collapsedconfiguration, and showing in phantom the shunt as it would be expandedin contact with the tissue wall;

FIGS. 11A-11C are perspective and elevational views of an alternativeexpandable shunt of the present application;

FIG. 12 is an elevational view of an exemplary puncture catheter havinga side-extending needle used to create a puncture in a sidewall of avessel, and FIGS. 12A-12C are enlarged views of elements thereof;

FIG. 13 is a vertical sectional view through a proximal handle of thepuncture catheter of FIG. 12;

FIG. 14A is an elevational view of a shunt deployment catheter of thepresent application showing interior components of a proximal handle,and FIG. 14B is an enlarged view of a distal end of the shunt deploymentcatheter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present application discloses methods and devices that allow forelevated Left Atrial Pressure (LAP) to be reduced by shunting blood fromthe left atrium to the coronary sinus. The primary method includesimplanting a shunt defining an open pathway between the left atrium andthe coronary sinus, although the method can be used to place a shuntbetween other cardiac chambers, such as between the pulmonary artery andright atrium. The shunt is expandable so as to be compressed, deliveredvia a low profile sheath or tube, and expelled so as to resume itsexpanded state. The method also includes utilizing a deployment catheterthat first creates a puncture in the wall between the left atrium andthe coronary sinus. Details of these methods, implants and deploymentsystems will be described below.

FIG. 1 illustrates several access pathways for maneuvering guidewiresand catheters in and around the heart to deploy expandable shunts of thepresent application. For instance, access may be from above via eitherthe subclavian or jugular veins into the superior vena cava (SVC), rightatrium (RA) and from there into the coronary sinus (CS). Alternatively,the access path may start in the femoral vein and through the inferiorvena cava (IVC) into the heart. Other access routes may also be used,and each typically utilizes a percutaneous incision through which theguidewire and catheter are inserted into the vasculature, normallythrough a sealed introducer, and from there the physician controls thedistal ends of the devices from outside the body.

FIG. 2 depicts one approach method for deploying the expandable shuntsdescribed herein, wherein a guidewire 10 is introduced through thesubclavian or jugular vein, through the superior vena cava and into thecoronary sinus. Once the guidewire provides a path, an introducer sheath(not shown) may be routed along the guidewire and into the patient'svasculature, typically with the use of a dilator. FIG. 2 shows adeployment catheter 12 extending from the superior vena cava to thecoronary sinus of the heart, the deployment catheter 12 having beenpassed through the introducer sheath which provides a hemostatic valveto prevent blood loss.

In one embodiment, the deployment catheter 12 may be about 30 cm long,and the guidewire 10 may be somewhat longer for ease of use. In someembodiments, the deployment catheter may function to form and prepare anopening in the wall of the left atrium, and a separate placement ordelivery catheter will be used for delivery of an expandable shunt. Inother embodiments, the deployment catheter may be used as the both thepuncture preparation and shunt placement catheter with fullfunctionality. In the present application, the terms “deploymentcatheter” or “delivery catheter” will be used to represent a catheter orintroducer with one or both of these functions.

Since the coronary sinus is largely contiguous around the left atrium,there are a variety of possible acceptable placements for the stent. Thesite selected for placement of the stent, may be made in an area wherethe tissue of the particular patient is less thick or less dense, asdetermined beforehand by non-invasive diagnostic means, such as a CTscan or radiographic technique, such as fluoroscopy or intravascularcoronary echo (IVUS).

FIGS. 3A-3V are schematic views of steps in making a puncture holethrough a wall of the coronary sinus and placement of a shunt betweenthe coronary sinus and left atrium, as seen looking down on a section ofthe heart with the posterior aspect down.

Initially, FIG. 3A shows a guidewire 20 being advanced from the rightatrium into the coronary sinus through its ostium or opening. A puncturecatheter 22 is then advanced over the guidewire 20, as seen in FIG. 3B.Specifics of an exemplary puncture catheter 22 will be shown anddescribed below with respect to FIGS. 12-13. The puncture catheter 22 isintroduced into the body through a proximal end of an introducer sheath(not shown). As is customary, an introducer sheath provides access tothe particular vascular pathway (e.g., jugular or subclavian vein) andmay have a hemostatic valve therein. While holding the introducer sheathat a fixed location, the surgeon manipulates the puncture catheter 22 tothe implant site.

At least a distal end of the puncture catheter 22 preferably has aslight curvature built therein, with a radially inner and a radiallyouter side, so as to conform to the curved coronary sinus. An expandableanchoring member 24 is exposed along a radially outer side of thecatheter 22 adjacent an extreme distal segment 25 that may be thinnerthan or tapered narrower from the proximal extent of the catheter.Radiopaque markers 26 on the catheter 22 help the surgeon determine theprecise advancement distance for desired placement of the anchoringmember 24 within the coronary sinus. Desirably, the radiopaque markers26 are C-shape bands that flank the proximal and distal ends of theanchoring member 24.

FIG. 3C shows radially outward deployment of the expandable anchoringmember 24, which in the illustrated embodiment as a bulbous balloon butcould also be a braided mesh. One advantage of a mesh is that it avoidsexcessive blockage of blood flow through the coronary sinus during theprocedure, though the procedure typically does not take very long and aballoon is preferred. Other possible anchoring structures includeNitinol stent like structures, nitinol wire structure, etc. Expansion ofthe anchoring member 24 presses the radially inner curve of the catheteragainst the luminal wall of the coronary sinus. Again, the expandableanchoring member 24 is located adjacent the distal segment 25 of thepuncture catheter 22, and expands opposite a needle port 28 formed inthe radially inner side wall of the catheter. Consequently, the needleport 28 abuts the luminal wall and faces toward a tissue wall 30 betweenthe coronary sinus and the left atrium. Preferably, guided byvisualizing the radiopaque markers 26, the surgeon advances the catheter22 so that the needle port 28 is located within about 2-4 cm into thecoronary ostia. This places the subsequent puncture approximately abovethe “P2” portion of the posterior leaflet of the mitral valve (whenlooking at the inflow side of the valve the posterior leaflet hasP1-P2-P3 cusps in a CCW direction, as seen in FIG. 3B). The anchoringmember 24 may be centered diametrically across the catheter 22 from theneedle port 28, or as shown may be slightly offset in a proximaldirection from the needle port 28 to improve leverage.

The curvature at the distal end of the puncture catheter 22 aligns toand “hugs” the anatomy within the coronary sinus and orients the needleport 28 inward, while the anchoring member 24 holds the catheter 22 inplace relative to the coronary sinus. Subsequently, as seen in FIG. 3D,a puncture sheath 32 having a puncture needle 34 with a sharp tipadvances along the catheter 22 such that it exits the needle port 28 atan angle from the longitudinal direction of the catheter and puncturesthrough the wall 30 into the left atrium. The puncture sheath 32 has abuilt-in curvature at the end that “aligns” with the curvature of theanatomy ensuring that the needle 34 is oriented inward toward the leftatrium. The anchoring member 24 provides rigidity to the system andholds the needle port 28 against the wall 30. Preferably, the punctureneedle 34 has a flattened configuration to form a linear incision, andis mounted on the distal end of an elongated wire or flexible rod (notshown) that passes through a lumen of the puncture sheath 32.

FIG. 3E illustrates proximal retraction of the puncture needle 34 fromwithin the puncture sheath 32. The puncture needle 34 is removedcompletely from the catheter 22, which leaves open a lumen within thepuncture sheath 32. FIG. 3F then shows advancement of a second guidewire36 through the puncture sheath 32 lumen and into the left atrium.Alternatively, the guidewire 36 passes through a lumen provided in thepuncture needle 34.

FIG. 3G illustrates removal of the puncture sheath 32 from the leftatrium and into the puncture catheter 22, which leaves just theguidewire 36 extending through the coronary sinus and into the leftatrium. During these steps, the anchoring member 24 remains expandedagainst the opposite luminal wall of the coronary sinus for stability.

FIG. 3H shows a puncture expander 40 advanced along the guidewire 36 andthrough the tissue wall 30 into the left atrium. The puncture expander40 may be an elongated inflatable balloon having a tapered distal end42.

FIG. 3I then shows retraction of the puncture catheter 22 from aroundthe elongated puncture expander 40. The puncture expander 40 and aproximal inflation tube 44 ride over the guide wire 36 and are held inplace during retraction of the catheter 22. The puncture catheter 22retracts just far enough to avoid interference with the expander 40.FIG. 3J illustrates radially outward inflation of the puncture expander40 so as to widen the puncture through the tissue wall 30.

FIG. 3K then shows retraction of the puncture expander 40 through theneedle port 28 and into the puncture catheter 22. Subsequently, theentire puncture catheter 22 is removed along the guide wire 36 from thebody, as seen in FIG. 3L. Although puncturing a hole between thecoronary sinus and the left atrium as well as delivering the shunt maybe accomplished with a single access device, the present methodcontemplates two different devices performing the separate tasks.

FIG. 3M thus shows introduction of a shunt deployment or deliverycatheter 50 having a soft, tapered distal tip 52 advancing along theguide wire 36 that remains bridging the tissue wall 30 between thecoronary sinus and the left atrium. FIG. 3N then shows the deliverycatheter 50 advanced through the puncture in the tissue wall 30 into theleft atrium, which passage is facilitated by widening of the puncture asdescribed above and the soft, tapered distal tip 52. The deliverycatheter 50 is shown in section in these views to illustrate a desiredposition of an expandable shunt 150 therein, just proximal to the distaltip 52. The expandable shunt 150 is shown in a collapsed, generallytubular configuration, described in more detail below, which facilitatespassage through the lumen 54 of the catheter 50. Actuating rodsextending through the lumen 54 and connected to the expandable shunt 50are not shown in some of these illustrations for clarity, but are alsodescribed below.

FIG. 3O depicts an initial deployment of the shunt 150 wherein a pair ofdistal flanges 152 expands within the left atrium into contact with thetissue wall 30. This expansion is initiated by retraction of an outersheath 60 of the delivery catheter 50 relative to an inner sheath 56. Aswill be described below with respect to FIG. 14B, the shunt 150 islocated in the annular space between the inner sheath 56 and outersheath 60. The inner sheath 56 passes through a central flow passage ofthe shunt 150. Typically, the shunt 150 collapses (is crimped) into agenerally tubular configuration between the two sheaths with the flangesstraightened, and its flanges spring open as seen in FIGS. 3O and 3Pwhen the restraining outer sheath 60 retracts. As will be describedbelow, the flanges 152 expand generally in opposite directions in acommon plane to form a T-shape, as opposed to expanding in a circularfashion which would form an annular flange. Radiopaque markers on theflanges 152 may be provided to facilitate positioning immediately withinthe left atrium.

FIG. 3P illustrates further deployment of the expandable shunt 150 justbefore a pair of proximal flanges 154 expands within the coronary sinusinto contact with the wall 30. More particularly, the physician retractsthe entire inner sheath 56 and shunt 150 until the two distal flanges152 come into contact with the tissue wall 30. This can be felt bytactile feedback, or by once again confirming the position of the distalflanges 152 by radiopaque visualization. The outer sheath 60 is alsoshown retracted farther proximally to expose a pair of proximal flanges154. At this stage in deployment of the shunt 150, the proximal flanges154 are retained by actuating rods and prevented from expanding withinthe coronary sinus.

FIG. 3Q is an enlarged view from the perspective of the coronary sinusto better illustrate deployment of the proximal flanges 154. Asdescribed above, the inner sheath 56 is retracted so that the distalflanges 152 are in intimate engagement with the tissue wall 30 on theleft atrial side. The proximal flanges 154 remain constrained generallyaligned with the inner sheath 56.

FIG. 3R shows distal advancement of a first control or actuating rod 162a from within the inner sheath 56. The first actuating rod 162 a emergesfrom a side opening 62 in the inner sheath 56, and is coupled to aleading or first proximal flange 154 a such that the flange is permittedto expand into its relaxed position as shown. Once the flange 150 isbelieved to be positioned within the puncture wound, but prior to itsrelease from the delivery catheter 50, a contrast injection is desirablymade in the vicinity to see whether the shunt is properly positioned.That is, contrast media visible in the gaps between the opposed flanges152, 154 indicates that the flanges are not on opposite sides of thetissue wall 30. The shunt 150 can thus be further manipulated tochanging position.

FIG. 3S then shows release of the first proximal flange 154 a by thefirst actuating rod 162 a, thus permitting the flange to resilientlycontact the tissue wall 30 (or at least the luminal surface of thecoronary sinus). The physician then causes retraction of the firstactuating rod 162 a into the side opening 62, as seen in FIG. 3T.Subsequently, a second control or actuating rod (not shown) releases thetrailing or second proximal flange 154 b, which also permits it toresiliently contact the tissue wall 30. At this point, the shunt 150 isentirely free from the delivery catheter 50, though the inner sheath 56remains extending through the central flow passage of the shunt. Theopposed leading flanges 152 a, 154 a form a clamping pair of flanges, asdo the opposed trailing flanges 152 b, 154 b. As will be explained, theclamping pairs of flanges apply a small compressive force to the tissuewall 30 hold the shunt 150 in place, though the gaps separating theclamping pairs of flanges is desirably calibrated to avoid excessiveclamping or necrosis of the tissue.

The delivery catheter 50 is shown being retracted along the guidewire 36in FIG. 3U, such that the shunt 150 is fully deployed between the leftatrium and the coronary sinus. The guidewire 36 is then retracted aswell. FIG. 3V illustrates full deployment with the proximal pair offlanges 154 expanded within the coronary sinus into clamping contactwith the wall 30. The primary retention mechanism for the shunt 150comes from the geometrical constraint of the design—the length of theflanges 152, 154 prevent it from being pulled through the hole.Secondary to that is a radial force exerted outward on the puncture fromthe central flow tube 166 of the implant (described below). The opposedclamping forces of the flanges 152, 154 also help hold the shunt 150 inplace, but are not essential. Elevated Left Atrial Pressure (LAP) canthus be ported through the implanted shunt 150 into the coronary sinusas indicated by the dashed arrow in FIG. 3V. By creating an openingbetween the left atrium and the coronary sinus, blood will flow from thehigher pressure left atrium (usually >8 mmHg) to the lower pressurecoronary sinus (usually <8 mmHg).

Previous methods (e.g., available from V-Wave Ltd. of Hod-Hasharon,Israel & Corvia Medical of Tewksbury, Mass. (previously DC Devices,Inc.)) to reduce LAP have instead utilized a shunt between the leftatrium and the right atrium, through the interatrial septumtherebetween. This is a convenient approach, as the two structures areadjacent and transseptal access is common practice. However, there isalways a possibility of emboli travelling from the right side of theheart to the left, which presents a stroke risk. This event should onlyhappen if the right atrium pressures go above left atrium pressures;primarily during discrete events like coughing, sneezing, Valsalvamaneuver, or bowel movements. The anatomical position of the septumwould naturally allow emboli to travel freely between the atria if ashunt was present and the pressure gradient flipped. This can bemitigated by a valve or filter element in the shunt, but there is stilla risk that emboli will cross over.

Shunting to the coronary sinus offers some distinct advantages,primarily that the coronary sinus is much less likely to have embolipresent for several reasons. First, the blood draining from the coronaryvasculature into the right atrium has just passed through capillaries,so it is essentially filtered blood. Second, the ostium of the coronarysinus in the right atrium is often partially covered by a pseudo-valvecalled the Thebesian Valve. The Thebesian Valve is not always present,but some studies show it is present in >60% of hearts and it would actas a natural “guard dog” to the coronary sinus to prevent emboli fromentering in the event of a spike in right atrium pressure. Third,pressure gradient between the coronary sinus and the right atrium intowhich it drains is very low, meaning that emboli in the right atrium islikely to remain there. Fourth, in the event that emboli do enter thecoronary sinus, there will be a much greater gradient between the rightatrium and the coronary vasculature than between the right atrium andthe left atrium. Most likely emboli would travel further down thecoronary vasculature until right atrium pressure returned to normal andthen the emboli would return directly to the right atrium.

Some additional advantages to locating the shunt between the left atriumand the coronary sinus is that this anatomy is less mobile than theseptum (it is more stable), it thus preserves the septum for latertransseptal access for alternate therapies, and it could potentiallyhave other therapeutic benefits. By diverting left atrial blood into thecoronary sinus, sinus pressures may increase by a small amount. Thiswould cause blood in the coronary vasculature to travel more slowlythrough the heart, increasing perfusion and oxygen transfer, which wouldbe more efficient and also could help a dying heart muscle to recover.There is a device designed to do this very thing, the Neovasc Reducer.The preservation of transseptal access also is a very significantadvantage because HF patients often have a number of other comorbiditieslike Atrial Fibrillation (AF) and Mitral Regurgitation (MR) and severalof the therapies for treating these conditions require a transseptalapproach.

The shunt 150 may also be positioned between other cardiac chambers,such as between the pulmonary artery and right atrium. The shunt 150 isdesirably implanted within the wall of the pulmonary artery using thedeployment tools described herein, with the catheters approaching fromabove and passing through the pulmonary artery. As explained above,pulmonary hypertension (PH) is defined as a rise in mean pressure in themain pulmonary artery. Blood flows through the shunt 150 from thepulmonary artery into the right atrium if the pressure differentialcauses flow in that direction, which attenuates pressure and reducesdamage to the pulmonary artery. The purpose is to attenuate pressurespikes in the pulmonary artery. The shunt 150 may also extend from thepulmonary artery to other heart chambers (e.g., left atrium) and/orblood vessels. Although not preferred or shown, the shunt 150 mayfurther contain a one-way valve for preventing backflow, or a checkvalve for allowing blood to pass only above a designated pressure.

The present application discloses a new expandable shunt, a tool forpreparing the wall between the left atrium and the coronary sinus forimplant of the shunt, and a tool for delivering the shunt. Each of thesedevices will be described below.

FIGS. 4A-4H illustrates a sequence of deployment of an exemplaryexpandable shunt 150 through a delivery tube or catheter 142. The shunt150 is expelled from the distal tip 144 of the catheter 142 andnaturally self-expands due to its inherent springiness or flexibility.In a preferred embodiment, the shunt 150 is formed from a super elasticmaterial such as Nitinol. The delivery catheter 142 in this sequence isshown as a tubular member from the distal end of which the shunt 150 isexpelled, unlike the catheter shown in the sequence of FIGS. 3N-3T,above, or in FIGS. 14A-14B below. It should be understood, therefore,that the expandable shunt 150 can be implanted and the various methodsdescribed herein can be performed using a number of different deliverycatheters.

FIGS. 4A-4D show the shunt 150 gradually advancing from the distal tip144 and expanding in stages. The reader will reference FIGS. 6A-6E for aclearer understanding of the various components of the expandable shunt150. In FIG. 4A, a terminal end 160 a of a leading or first distalflange 152 a is seen emerging distally from the catheter 142 followed bythe rest of the flange in FIG. 4B. FIG. 4B shows a terminal end 160 b ofa trailing or second distal flange 152 b emerging from the catheter 142.FIG. 4C shows the second distal flange 152 b curling in a proximaldirection due to its inherent shape memory, while the first distalflange 152 a continues to extend in a distal direction. Eventually, boththe first and second distal flanges 152 a, 152 b are fully expelled fromthe catheter 142 and extend generally in opposite directions, as shownin FIG. 4D. The first distal flange 152 a is longer than the seconddistal flange 152 b.

It should be noted that the location of the distal tip 144 of thecatheter 142 enables deployment of the first and second distal flanges152 a, 152 b within the left atrium. In this way, the flanges 152 a, 152b may be expanded into contact with the wall 30 on the left atrial side.Subsequently, the catheter 142 is retracted until the distal tip 144 islocated in the coronary sinus, and then the proximal flanges 154 may bedeployed, as will be explained. (The reader will notice that the shunt150 in these views is inverted from the delivery sequence of FIGS.3N-3V, such that the distal flanges 152 a, 152 b are down while theproximal flanges 154 a, 154 b are up.) The offset lengths of the opposedflanges 152, 154 reduces excessive pinching of the tissue wall 30therebetween.

FIG. 4D also shows a first control or actuating rod 162 a projectingfrom the distal tip 144 of the catheter 142. The first actuating rod 162a and a second control or actuating rod 162 b, seen first in FIG. 4E,engage different locations on the expandable shunt 150 and control itsexpulsion from the catheter 142. The first actuating rod 162 a engages aterminal end 164 a of a leading or first proximal flange 154 a, whilethe second actuating rod 162 b engages a terminal end 164 b of atrailing or second proximal flange 154 b. The first proximal flange 154a is shorter than the second proximal flange 154 b. The first and secondactuating rods 162 a, 162 b are configured to slide axially within thecatheter 142 independently of one another. Various mechanisms are knownfor displacing such rods along catheters and thus will not be describedin detail herein.

As seen in FIGS. 4F and 4G, the first actuating rod 162 a continues toadvance the terminal end 164 a of the first proximal flange 154 a, butthe second actuating rod 162 b halts so as to stop advancement of theterminal end 164 b (see FIG. 4H) of the second proximal flange 154 b.This permits the two flanges 154 a, 154 b to separate so as to allow theshunt 150 to assume its relaxed, expanded configuration. Moreparticularly, a central flow tube 166 (or “barrel” portion) graduallyopens until the fully expanded state is reached. The two actuating rods162 a, 162 b may carry thin elongated release rods 178 which may beretracted to release the rods from engagement with the proximal flanges154 a, 154 b.

FIG. 4H shows the shunt 150 in its fully expanded state just afterdetachment of the two actuating rods 162 a, 162 b. The distal andproximal flanges 152, 154 secure the shunt 150 on opposite sides of thewall 30 between the coronary sinus and the left atrium (see FIGS. 3U and3V), with a flow axis of the central flow tube 166 aligned generallyperpendicular to the wall so as to maintain an open flow path betweenthe coronary sinus and the left atrium.

FIGS. 5A-5C are several views of the expandable shunt 150 beingretracted into the delivery catheter 142. In case the placement of theshunt 150 fails or is unsatisfactory, and before the first and secondactuating rods 162 a, 162 b detach therefrom, the shunt can beretrieved. In particular, proximal movement of the first actuating rod162 a as seen in FIG. 5A pulls the first proximal flange 154 a so as tostart collapse of the shunt. Further retraction of the first actuatingrod 162 a and then of the second actuating rod 162 b as seen in FIGS. 5Band 5C continues the collapse, essentially in the reverse of thedeployment steps of FIGS. 4A-4G. Placement of the shunt 150 may then beretried, or a different shunt used altogether by replacement of theentire deployment system.

FIGS. 6A-6D show greater details of the exemplary expandable shunt 150in an expanded configuration, while FIG. 6E is a view looking throughthe central flow tube 166 along an angle of tilt. When expanded, thecentral flow tube 166 of the shunt 150 defines a generally circular oroval opening, as seen from above in FIG. 6D, which holds the sides ofthe puncture open and forms the blood flow path between the coronarysinus and the left atrium. The central flow tube 166 is partly formed bya pair of side walls 170 a, 170 b defined by a generally parallelogramarrangement of thin struts 179 that forms an array ofparallelogram-shaped cells or openings 180. Indeed, the entire shunt 150is formed by super-elastic struts that are capable of compression intothe catheter 142 and subsequent expansion back to the relaxed shape asshown.

Formation of the shunt 150 using a plurality of interconnected strutsforming cells therebetween is primarily to increase the flexibility ofthe shunt which enables it compression and then expansion at the implantsite. The interconnected struts around the central flow tube 166 providea cage of sort which is sufficient to hold the tissue at the punctureopen. Desirably, the interconnection of the struts omits any sharpcorners or points which might snag tissue when the shunt is beingmanipulated through the puncture.

End walls 172 a, 172 b of the central flow tube 166 connect the sidewalls 170 a, 170 b and extend between the distal and proximal flanges152, 154 on each side. The side walls 170 a, 170 b and end walls 172 a,172 b together define a tubular lattice which as will be seen is angledor tilted. The end walls 172 a, 172 b also comprise thin struts 179extending at a slight angle from a perpendicular axis 174 through thecentral flow tube 166. That is, as seen in FIG. 6C, an imaginaryreference axis 174 may be drawn generally perpendicular to a horizontalreference plane HP, such that an angled axis 176 is defined by theangled end walls 172 a, 172 b of the central flow tube 166. Indeed, thecentral flow tube 166 extends at an angle α from the perpendicular axis174. The angle α may be between 30-60°, and more particularly is about45°. The horizontal reference plane HP is generally defined by the wall30 between the coronary sinus and the left atrium (FIG. 3U); though ofcourse the wall is not simply planar. Although oriented at this slightangle α, the opening as seen in FIG. 6D formed by the central flow tube166 is generally perpendicular to the wall 30 and permits direct bloodflow between the coronary sinus and the left atrium. That is, the angledflow tube 166 is wide and short enough such that proper shunting occurs,as if the flow tube were perpendicular to the tissue wall 30.

FIG. 6E is a view looking along angled axis 176 of the central flow tube166 of the expanded shunt 150. The axis 176 defines the “tilt” of theexpanded shunt 150, in that it defines the angle that the central flowtube 166 makes with the horizontal reference plane HP, which again liesgenerally in the plane of the tissue wall through which the shuntpasses. It can thus be seen from FIG. 6E that the struts of the centralflow tube 166 define a tubular or circular lattice, even if the strutsthat form the tube do not form a contiguous wall surface (there are opencells). The tilt of the expandable shunt 150 facilitates collapse intothe delivery catheter 142, and then expansion of the flanges 152, 154 onboth sides of the tissue wall 30. It should be noted that the centralflow tube 166 remains essentially unchanged between the collapsed andexpanded states of the shunt 150, whereas the flanges 152, 154transition in and out of alignment with the angled flow tube.

FIG. 6F is a view similar to FIG. 6E through an alternative shunt havingan oval-shaped flow tube 166′. The characteristics of the shunt are thesame as with the shunt 150, though the side walls are elongated incomparison to form the oval channel. This alternative may be useful forlarger punctures while the shunt still collapses down to a relativelysmall delivery profile. An oval-shaped delivery catheter may be used todeploy the shunt or a standard tubular catheter is used with the shuntconforming therein.

Referring back to FIG. 6C, each of the distal and proximal flanges 152,154 curls outward from the end walls 172 a, 172 b and ends up pointingapproximately radially away from the imaginary reference axis 174through the central flow tube 166. More specifically, the two distalflanges 152 a, 152 b extend away from each other as do the two proximalflanges 154 a, 154 b. As seen best in FIG. 6D, the flanges 152, 154extend outward from the central flow tube 166 in opposite directionsparallel to a central vertical plane VP, such that the shunt 150 isgenerally elongated longitudinally but is relatively narrow laterally.Stated another way, the distal and proximal flanges 152, 154 are notannular/circular but instead extend outward generally in only one plane.FIG. 6C shows that each pair of flanges 152, 154 forms somewhat of aT-shape on that end of the central flow tube 166, and the entire sideview resembles a sideways H-shape. This is in contrast to a spool shapewhich would be the case if the flanges were annular. This elongated orlinear shape for the expandable shunt 150 means that when compressed itelongates along a line so as to better fit within the catheter 142. Ofcourse, the struts of the super-elastic flanges 152, 154 are curved, notsolid and not geometrically precise, but what they are clearly not isannular/circular. Likewise, the central flow tube 166 is tilted asopposed to extending straight between the flanges 152, 154, but theH-shaped analogy remains.

As indicated in FIG. 6D, the shunt 150 has a maximum lateral width Wapproximately equal to the diameter of the central flow tube 166, whilethe lateral width w of the flanges 152, 154 is slightly less. In oneembodiment, the maximum lateral width W of the shunt 150 is about 7.5mm, while the lateral width w of the flanges 152, 154 is about 7.0 mm.

As seen best from above in FIG. 6D, each flange 152, 154 has a somewhattriangular plan view shape with a wide base at the central flow tube 166narrowing to an apex at the terminal ends 160, 164. The elongated shapeof the shunt 150 permits it to collapse down to a more linear profile soas to fit within a relatively small catheter 142. The reader will noticethat the distal and proximal flanges 152, 154 are entirely curved inconfiguration which also facilitates their collapse and expansion. Thatis, the struts that form the flanges 152, 154 are designed so that theyeasily collapse into a compact size that fits into the catheter 142 whenacted on by the first and second actuating rods 162 a, 162 b. Finally,the shunt 150 is inversely symmetrical across the horizontal plane HP inFIG. 6C, which is also a midplane of the shunt. That is, the firstdistal flange 152 a is generally the same size and shape as the secondproximal flange 154 b, and the first proximal flange 154 a is generallythe same size and shape as the second distal flange 152 b, and so on.

Additionally, each pair of distal and proximal flanges 152, 154 on eachside of the central flow tube 166 converges toward each other so thattheir terminal ends 160, 164 are closer together than the ends connectedto the end walls 172 a, 172 b. This enables the end walls 172 a, 172 bto have a length that approximates thickness of the wall 30 between thecoronary sinus and the left atrium (see FIG. 3V). The terminal ends 160,164 of the flanges 152, 154 are spaced closer together so that they flexoutward and grip the wall, thus helping to maintain the shunt 150 inplace. FIG. 3V shows the terminal ends 160, 164 squeezing the tissuewall 30. Of course, the super-elasticity of the flanges 152, 154 meansthey are highly flexible and so they will not apply excessive clampingforces to the wall 30 which might cause necrosis. Furthermore, theoffset lengths of the opposed flanges 152, 154 reduces direct pinchingof the tissue wall 30 therebetween.

The terminal ends 164 of the proximal flanges 154 are shaped for rapidengagement with the first and second actuating rods 162 a, 162 b. Inparticular, the terminal ends 164 a, 164 b each define an eyehole orother closed shape so as to be easily gripped by the first and secondactuating rods 162 a, 162 b. In the illustrated embodiment, each of theterminal ends 164 a, 164 b defines a generally rectangular closed holethrough which a slim rod may be passed. Although not shown in greatdetail, FIGS. 4E and 4F show the slim release rods 178 passed throughthe ends 164. An engagement portion of each of the first and secondactuating rods 162 a, 162 b provides a hook, notch or recess shaped toclosely receive and hold the terminal ends 164 a, 164 b when the slimrods 178 are thus engaged. To release the terminal ends 164 a, 164 b,the slim rods 178 are retracted relative to the remainder of theactuating rods 162, as seen in FIG. 4H. Of course, numerous otherconfigurations of this gripping arrangement may be utilized, theillustrated embodiment being exemplary only.

FIGS. 7A and 7B are elevational views of the exemplary expandable shuntillustrating certain preferred dimensions and advantageous structuralfeatures. An overall length L of the shunt 150 may vary, and in oneembodiment is between about 25-30 mm, preferably 28±1 mm. Theperpendicular reference axis 174 extends through a central point in theside walls 170 and can be used to quantify the lengths of each of theflanges 152, 154. There is a shorter pair and a longer pair of flanges,one on each side of the horizontal midplane HP. A first length L₁ of theshorter pair of flanges is between about 9-13 mm, preferably 11±0.7 mm.This length is believed to be short enough to enable the shorterproximal flange 154 to rotate almost 180° within the coronary sinus. Asecond length L₂ of the longer pair of flanges is between about 12-16mm, preferably 14±0.5 mm. The length of the longer distal flange 152 ispreferably limited to avoid touching the mitral valve leaflet. It shouldbe noted that the terminal ends of the shorter flanges end upapproximately parallel to the horizontal midplane HP, while the terminalends of the longer flanges may also be parallel but are preferably areangled slightly away from the horizontal midplane HP by an angle θ ofbetween 0-20°.

FIG. 7A also shows various vertical dimensions of the expanded shunt150, including an overall height H of between about 5-10 mm, morepreferably about 6.7±1.0 mm. A first height dimension H₁ of the longerpair of flanges from the midplane HP is between 3-5 mm, more preferablyabout 3.4 mm, while a second height dimension H₂ of the shorter pair offlanges is between 2-4 mm, more preferably about 2.4±0.5 mm. A gap Gformed between the terminal ends of each pair of opposed flanges isbetween about 0-5 mm, and more particularly about 1.25±1.5 mm. It shouldbe noted that even with a gap G of 0 mm, the two opposed flanges areindependently deployed on opposite sides of the tissue wall, which maybe relatively thin. It is expected that the tissue wall 30 has athickness of between about 2-4 mm, and the gap G will be dimensionedaccordingly. Finally, a height dimension h of the central flow tube 166(as defined by the height of the side walls 170) is between 3-5 mm, andmore particularly about 3.9±0.2 mm.

FIG. 7B is another elevational view of the expanded shunt 150 whichillustrates a preferred configuration of the thin struts 179 making upthe central flow tube 166. As mentioned above, the flow tube 166 isdefined by a generally parallelogram arrangement of struts that forms anarray of parallelogram-shaped cells or openings 180. The side walls 170are generally circumscribed by a large parallelogram 182 that is tiltedin the same direction as the tilted axis 176 through the central flowtube. Indeed, each of the cells 180 is tilted in the same direction.However, there are two rows of three cells 180 each stacked along thecentral axis 176 that are offset lengthwise from each other such thatthere are spaces in the struts on the opposite obtuse corners of theparallelogram 182. Specifically, as highlighted, a lower cell row 184 aextends to the left end wall 172 a but there is a space 186 a between itand the right end wall 172 b. Conversely, an upper cell row 184 bextends to the right end wall 172 b but defines a space 186 b between itand the left end wall 172 a. Consequently, the right end wall 172 bdirectly connects only to the upper row 184 b of cells while the leftend wall 172 a directly connects only with the lower row 184 a of cells.These spaces facilitate collapse of the shunt 150 for delivery throughthe catheter as described herein.

FIG. 8A is a flattened view of the expandable shunt 150 as if a shunthad been severed along one of the end walls 172 and along the midline ofthe associated flanges 152, 154. This view illustrates orientations ofthe parallelogram-shaped cells 180 in the side walls 170 relative toparallelogram-shaped cells 188 in the end walls 172. Once again, theupper and lower cell rows 184 a, 184 b in one of the side walls 170 arehighlighted. The parallelogram-shaped cells 180 in these rows are angledin one direction, in this case in a clockwise tilt. The adjacent cell188 in the end wall 172 is on the other hand angled in the oppositedirection, with a counterclockwise tilt. This is also seen clearly inthe adjacent perspective view of FIG. 8D. This beneficial juxtapositionof the oppositely-tilted cells 180, 188 facilitates collapse of theshunt 150. That is, the super elastic material making up the strutseasily flexes into an elongated shape, as will be seen below withrespect to FIGS. 9A-9D.

FIGS. 8A-8C also shows several dimensions and a preferred configurationfor the terminal ends 160, 164 of the flanges. In one embodiment, aspacing S across the struts that define the cells 180, 188 is between1.5-2.5 mm, and preferably about 1.6 mm. The thickness t of the strutsthat define the cells 180, 188 is at least 0.2 mm, preferably between0.2-0.3 mm. The terminal ends 164 of each proximal flange 154 defines abuckle 190, seen enlarged in FIG. 8B. The buckles 190 are provided onthe terminal ends 164 of the proximal flanges 154 so that they may beengaged by the first and second actuating rods 162, as described above.Each buckle 190 desirably comprises a generally rectangular peripherywith a rectangular aperture 192 therein. A width dimension W₁ of eachbuckle 190 is desirably between 2-3 mm, and preferably about 2.7 mm.FIG. 8B also shows slightly thicker struts 194 having a thicknessdimension T of between 0.4-0.5 mm, which are utilized on the outer edgesof the flanges 152, 154. The terminal ends 160 of the distal flanges152, as seen in FIG. 8C, are shaped as elongated rectangles havingrectangular cutouts 196 to reduce their stiffness. The apertures 192 inthe buckles 190 also increase their flexibility, and the flexibleterminal ends 160, 164 are therefore less traumatic to the tissue wall30.

With respect to FIG. 8A, the different strut configuration of theflanges 152 a, 154 a are detailed. As seen in the partial perspective ofFIG. 8D, the two opposed clamping flanges on each longitudinal side ofthe central flow tube 166 extend away in the same direction from thecorresponding end wall 172 a. FIG. 8A shows, however, that the proximalflange 154 a, in this case the shorter flange, comprises both thinstruts 179 and thick struts 194 that extend from the end wall 172 a (orat least from a junction of the end wall 172 a and side walls 170),whereas the longer distal flange 152 a has thin struts 179 that connectto the end wall 172 a and thick struts 194 that connect to the sidewalls 170. Conversely, the flanges 152 b, 154 b located 180° around thecentral flow tube 166 are configured similarly but the longer strut ison the proximal end while the shorter strut is on the distal end. Onboth ends it is the shorter strut that connects just to the end wall 172and thus is more flexible. That is, the struts of the shorter proximalflange 154 a converge toward each other at the end wall 172 a, as seenin FIG. 8A, which reduces the lateral size of the hinge about which theypivot when they convert from their elongated state within the catheterto their bent shape when implanted. The longer distal flange 152 a alsorotates outward when released but not quite as far as the shorterflange. This difference in movement can best be seen in FIG. 10, and canbe summarized by noting that when the shunt 150 expands, the shorterflanges rotate outward more than 90° while the longer flanges rotateless than 90°.

It should be understood that the various struts that form the shunt 150are desirably fabricated by laser cutting a Nitinol tube. The tubedesirably has a wall thickness of between about 0.1-0.3 mm, andpreferably about 0.2 mm. A preferred method for cutting the shape of theshunt 150 will become clearer below with respect to the collapsed viewsof FIGS. 9A-9D.

FIGS. 9A-9D are perspective and orthogonal views of the exemplaryexpandable shunt 150 in a collapsed configuration for delivery throughan access sheath or catheter. In this configuration, the shunt 150describes a tubular form. That is, the flanges 152, 154 form extensionsof the end walls 172, and together with the side walls 170 form a tube.Indeed, this is the shape that the shunt 150 has immediately after beinglaser cut from a tubular workpiece. The laser passes across the tube atan angle parallel to the reference plane P shown in FIG. 9B. Moreover,the laser is programmed to move along a flat pattern such as shown inFIG. 8A wrapped around the tube. The resulting tubular form of the shunt150 may then be deformed using mandrels and the like to bend the flanges152, 154 outward into the configuration shown, for example, in FIGS. 6Aand 6B. The shunt 150 in its deformed shape is then heat treated suchthat the Nitinol material reaches a transition temperature and theexpanded shape becomes the relaxed shape. However, the Nitinol can thenbe easily reformed by bending into the tubular shape of FIGS. 9A-9D forloading within the delivery catheter.

FIG. 10 is a schematic view of a delivery catheter such as that shown at50 in FIGS. 3N-3T passing at an angle through a tissue wall 30 with theexemplary expandable shunt 150 therein in a collapsed configuration, aswas shown in FIGS. 9A-9D. The shunt 150 is also shown in phantom as itwould be expanded in contact with the tissue wall 30. This clearlyillustrates the advantageous tilted configuration of the struts andcells of the side walls 170 of the shunt 150 which are oriented alongangled axis 176. The axis 176 coincides with the longitudinal axis ofthe delivery catheter 50, which passes through a puncture hole angled inthe same direction through the tissue wall 30. In this way, the shunt150 can be implanted in the tissue wall 30 using a catheter 50 thatpasses through at an angle. Once expanded, as seen in dashed line, theflanges 152, 154 clamp about the tissue wall 30 and maintain the centralflow tube 166 within the puncture wound. Furthermore, as mentionedabove, when the shunt 150 expands, the shorter flanges (154 a, 152 b)bend outward more than 90° while the longer flanges (152 a, 154 b) bendless than 90°.

FIGS. 11A-11C are perspective and elevational views of an alternativeexpandable shunt 150′ of the present application. This configurationalso features distal and proximal flanges 152′, 154′, and a central flowtube 166′. The flow tube 166′ is somewhat shallower than the firstembodiment, and the flanges 152′, 154′ have slightly different shapes,but the overall configuration is similar and again facilitates collapseinto the catheter 142. One primary difference is the provision offingers 180 on either end wall of the central flow tube 166′ extendingin opposite directions that help define and maintain open the blood flowpath.

FIGS. 12 and 12A-12C are a number of views of an exemplary puncturecatheter 222 having a side-extending needle used to create a puncture ina sidewall of a vessel, much as described above with respect to thepuncture catheter 22 of FIGS. 3A-3L. The puncture catheter includes anelongated, flexible hollow sheath 221 that extends to a curved distalportion terminating in an extreme distal segment 225. The curved distalportion is shown enlarged in FIG. 12A, and includes an expandableanchoring member 224 on an outer radial side opposite a side-extendingpuncture sheath 232 having a sharp puncture needle 234. The puncturesheath 232 projects through a side port (not shown) on an inner radialside. As explained above, the puncture needle 232 comprises an elongatedflexible or wire having a sharp distal tip. A pair of radiopaque markers226 flank the anchoring member 224 and locate the side port from whichthe puncture sheath 232 emerges.

FIG. 13 is a vertical sectional view through a proximal handle 240 ofthe puncture catheter 222 of FIG. 12C. The hollow sheath 221 of thepuncture catheter 222 defines several internal pathways or lumens (notnumbered) for at least the elongated puncture sheath 232 and a guidewire220 (such as guide wire 20 in FIG. 3A). The proximal handle 240 definesY-shaped internal channels such that the puncture sheath 232 continuesstraight out of the hollow sheath 221 and to a pusher or advancer 242,while the guidewire 220 passes through a divergent port which leads to aproximal luer fitting 244. The luer fitting 244 provides means forflushing the entire guidewire channel/lumen. The puncture sheath 232 isfixed within the needle advancer 242 which is arranged to slide in aproximal-distal direction through a rear bracket 246. When the needleadvancer 242 is displaced distally, the puncture sheath 232 slidesthrough a locking nut 248 that is fixed with respect to a forwardbracket 249. The locking nut 248 enables the advancer 242 and puncturesheath 232 to be fixed relative to the handle 240. In this way, thephysician can project or retract the puncture sheath 232 from the sideopening of the catheter 222, and fix its position in either location.

An inner needle 235 passes through the puncture sheath 232 andterminates in the sharp puncture needle 234. As seen in FIG. 13, theinner needle 235 extends from the rear of the puncture sheath 232 and isfixed within a hollow fitting 236. The hollow fitting 236, in turn, fitsclosely and is sealed within a proximal junction 243 on the advancer242. By pulling out the hollow fitting 236, the inner needle 235 may beretracted into and then removed from the puncture sheath 232 afterforming the puncture. This leaves the lumen of the puncture sheath 232open for passage of the second guidewire 36 (see FIG. 3F) that entersthe left atrium. Also, the puncture sheath 232 may be removed completelyand replaced with the puncture expander 40 used to widen the puncturebetween the coronary sinus and left atrium, as seen in FIGS. 3H-3J.

FIG. 14A is an elevational view of a shunt deployment catheter 250 ofthe present application showing interior components of a proximal handle264, and FIG. 14B is an enlarged view of a distal end thereof having asoft curved distal tip 252. As described above, the expandable shunt 150is carried on an inner sheath 256 over which concentrically slides anouter sheath 260. The shunt 150 collapses down primarily within a pairof opposed side recesses or openings 262 so that the sheath 260 canslide over it and maintain it in its collapsed configuration. The shunt150 mounts in its collapsed configuration with its central axis 176 (seeFIG. 6C) therethrough coinciding with a longitudinal axis of the innersheath 256 at the recesses 262.

The outer sheath 260 passes into the proximal handle 264, and the innersheath 256 continues and is fixed therein. A sliding mechanism 266surrounds and fastens to the outer sheath 260, and initiates axialmovement relative to the inner sheath 256. A pair of flexible arms 268project from a rear end of the handle 264 and connect to a pair ofactuating rods (such as actuating rods 162 a, 162 b shown in FIGS.4A-4H) that extend through the inner sheath 2564 manipulation of theexpandable shunt 150. Controlled release of the shunt 150 may thus bedone manually by the physician, or the actuating rods may be attached toseparate sliders on the handle 264.

FIG. 14B shows the end of the deployment catheter 250 after the sheath260 retracts. Initially, the shunt 150 may be compressed (crimped) downto its generally tubular configuration and held in the annular spacebetween the inner sheath 256 and outer sheath 260 with the flangesstraightened. Some smaller-sized shunts may not require crimping, andwhen the sheath 260 retracts only the flanges 152, 154 “expand.” Theside openings 262 provide recesses for the shunt flanges 152, 154, aswell as a portion of the actuating rods 162 a, 162 b, to lie against theinner sheath 256. When the outer sheath 260 retracts the central flowtube 166 of the shunt 150 expands and the flanges 152, 154 are permittedto expand, though the proximal flange are controlled by the actuatingrods 162 a, 162 b.

While the foregoing is a complete description of the preferredembodiments of the invention, various alternatives, modifications, andequivalents may be used. Moreover, it will be obvious that certain othermodifications may be practiced within the scope of the appended claims.

What is claimed is:
 1. An expandable blood flow shunt formed of anelastic material and configured to be inserted into a puncture wound ina tissue wall between two anatomical chambers and expand from acollapsed state to an expanded state to maintain a blood flow openingtherebetween, the tissue wall defining a reference plane generallyperpendicular to the opening, the shunt comprising, in an expandedstate: a central flow tube defined by an opposed pair of lateral sidewalls formed by struts extending between an opposed pair of end wallsformed by struts, the central flow tube defining a central axistherethrough angled from a reference axis extending perpendicularthrough the reference plane; two distal flanges formed by struts eachattached to a first axial end of the central flow tube, the distalflanges extending away from one another in opposite longitudinaldirections generally parallel to the reference plane; and two proximalflanges formed by struts each attached to a second axial end of thecentral flow tube opposite the first end, the proximal flanges extendaway from one another in opposite longitudinal directions generallyparallel to the reference plane, the proximal flanges extend in the samedirections as the distal flanges such that each proximal flangeparallels one of the distal flanges to form a clamping pair of flangeswith a gap therebetween sized to clamp onto the tissue wall.
 2. Theshunt of claim 1, wherein the struts of each of the proximal and distalflanges are curved such that the flanges in each clamping pair offlanges initially curve away from each other and then converge towardeach other at a terminal end thereof.
 3. The shunt of claim 1, whereineach clamping pair of flanges includes flanges of different lengths. 4.The shunt of claim 1, wherein the shunt has a maximum lateral widthdefined by the central flow tube.
 5. The shunt of claim 1, wherein thecentral flow tube viewed along its central axis is circular.
 6. Theshunt of claim 1, wherein when the shunt transitions from the collapsedto the expanded state a first flange in each clamping pair of flangesrotates outward more than 90° and a second flange in the same clampingpair of flanges rotates outward less than 90°.
 7. The shunt of claim 1,wherein the struts of the lateral side walls form connectedparallelograms defining open cells therein.
 8. The shunt of claim 7,wherein each side wall includes upper and lower rows ofparallelogram-shaped cells defined by the corresponding struts andstacked along the central axis, wherein the upper row connects to afirst end wall only and the lower row connects to a second end wallonly.
 9. An expandable blood flow shunt formed of an elastic materialand configured to be inserted into a puncture wound in a tissue wallbetween two anatomical chambers and expand from a collapsed state to anexpanded state to maintain a blood flow opening therebetween, the tissuewall defining a reference plane generally perpendicular to the opening,the shunt comprising, in an expanded state: a central flow tube definedby an opposed pair of lateral side walls formed by struts extendingbetween an opposed pair of end walls formed by struts, the side wallsand end walls together defining a tubular lattice and the central flowtube defining a central axis therethrough; two distal flanges formed bystruts connected to struts in the central flow tube at a first axial endthereof, the distal flanges extending away from one another in oppositelongitudinal directions generally parallel to the reference plane,wherein there is one long and one short distal flange; and two proximalflanges formed by struts connected to struts in the central flow tube ata second axial end thereof opposite the first end, the proximal flangesextending away from one another in opposite longitudinal directionsgenerally parallel to the reference plane, wherein there is one long andone short proximal flange, the proximal flanges extending in the samedirections as the distal flanges such that each proximal flangeparallels one of the distal flanges to form a clamping pair of flangeswith a gap therebetween sized to clamp onto the tissue wall, and whereinthe long distal flange and the short proximal flange form a clampingpair and the short distal flange and the long proximal flange form aclamping pair.
 10. The shunt of claim 9, wherein the struts of each ofthe proximal and distal flanges are curved such that the flanges in eachclamping pair of flanges initially curve away from each other and thenconverge toward each other at a terminal end thereof.
 11. The shunt ofclaim 9, wherein the shunt has a maximum lateral width defined by thecentral flow tube.
 12. The shunt of claim 9, wherein the central flowtube viewed along its central axis is circular.
 13. The shunt of claim9, wherein when the shunt transitions from the collapsed to the expandedstate a first flange in each clamping pair of flanges rotates outwardmore than 90° and a second flange in the same clamping pair of flangesrotates outward less than 90°.
 14. The shunt of claim 9, wherein thestruts of the lateral side walls form connected parallelograms definingopen cells therein.
 15. The shunt of claim 14, wherein each side wallincludes upper and lower rows of parallelogram-shaped cells defined bythe corresponding struts and stacked along the central axis, wherein theupper row connects to a first end wall only and the lower row connectsto a second end wall only.
 16. The shunt of claim 9, wherein the centralaxis is angled from a reference axis extending perpendicular through thereference plane.
 17. An expandable blood flow shunt formed of an elasticmaterial and configured to be inserted into a puncture wound in a tissuewall between two anatomical chambers and expand from a collapsed stateto an expanded state to maintain a blood flow opening therebetween, thetissue wall defining a reference plane generally perpendicular to theopening, the shunt comprising, in an expanded state: a central flow tubecomprising an opposed pair of lateral side walls formed by struts thatdefine open cells extending between an opposed pair of end walls formedby struts that define open cells, the side walls and end walls togetherdefining a tubular lattice and the central flow tube defining a centralaxis therethrough, wherein each side wall includes upper and lower rowsof cells defined by the corresponding struts stacked along the centralaxis; two distal flanges formed by struts connected to struts in thecentral flow tube at a first axial end thereof, the distal flangesextending away from one another in opposite longitudinal directionsgenerally parallel to the reference plane; and two proximal flangesformed by struts connected to struts in the central flow tube at asecond axial end thereof, the proximal flanges extending away from oneanother in opposite longitudinal directions generally parallel to thereference plane, the proximal flanges extending in the same directionsas the distal flanges such that each proximal flange parallels one ofthe distal flanges to form a clamping pair of flanges with a gaptherebetween sized to clamp onto the tissue wall, and wherein the tworows of cells in each side wall stop short of the opposed end walls ofthe central flow tube to define spaces therebetween such that a firstend wall directly connects only to the upper row of cells while a secondend wall directly connects only with the lower row of cells.
 18. Theshunt of claim 17, wherein the struts of each of the proximal and distalflanges are curved such that the flanges in each clamping pair offlanges initially curve away from each other and then converge towardeach other at a terminal end thereof.
 19. The shunt of claim 17, whereineach clamping pair of flanges includes flanges of different lengths. 20.The shunt of claim 17, wherein the shunt has a maximum lateral widthdefined by the central flow tube.
 21. The shunt of claim 17, wherein thecentral flow tube viewed along its central axis is circular.
 22. Theshunt of claim 17, wherein when the shunt transitions from the collapsedto the expanded state a first flange in each clamping pair of flangesrotates outward more than 90° and a second flange in the same clampingpair of flanges rotates outward less than 90°.
 23. The shunt of claim17, wherein the open cells are parallelogram-shaped.